docs: contributing document creation (#664)

Co-authored-by: Matthew Dent <[email protected]>

Author: mttdnt

CONTRIBUTING.md

@@ -0,0 +1,66 @@
+# Contributing to Sanity App SDK
+
+## Table of Contents
+
+- [Getting Started](#getting-started)
+- [Setup](#setup)
+- [Testing](#testing)
+- [Contributing](#contributing)
+
+## Getting Started
+
+Before contributing, please read our [code of conduct](https://github.com/sanity-io/.github/blob/main/CODE_OF_CONDUCT.md).
+
+### Prerequisites
+
+- Node.js: Version 20.x or higher (we recommend using the LTS version)
+- pnpm: Version 8.x or higher
+
+Check your versions:
+
+```bash
+node --version
+pnpm --version
+```
+
+## Setup
+
+1. Clone the repository
+
+```bash
+git clone [email protected]:sanity-io/sdk.git
+```
+
+2. Install dependencies
+
+```bash
+pnpm install
+```
+
+3. Run locally
+
+```bash
+pnpm run dev
+```
+
+## Testing
+
+Run tests locally before submitting:
+
+```bash
+pnpm test
+```
+
+## Contributing
+
+### Branch Guidelines
+
+We follow the [Conventional Branch](https://conventional-branch.github.io/) specification.
+
+### Commit Guidelines
+
+We follow the [Conventional Commits](https://www.conventionalcommits.org/) specification.
+
+### Pull Request Process
+
+Please follow the [Pull Request Template](.github/PULL_REQUEST_TEMPLATE.md) when submitting code for review.